A339699 Numbers m such that 3^m-1 and 3^m+1 have the same number k of prime factors counted with multiplicity.

5, 23, 25, 31, 41, 43, 47, 53, 67, 101, 109, 113, 127, 137, 141, 149, 155, 187, 191, 195, 203, 209, 253, 275, 317, 322, 329, 367, 389, 409, 415, 503, 537, 565, 613, 623, 637, 643

Offset

1,1

Comments

Corresponding values of k: {3, 3, 5, 4, 4, 3, 4, 4, 4, 6, 9}.

Links

Table of n, a(n) for n=1..38.

Example

3^5 - 1 = 242 = 2*11*11, 3^5 + 1 = 244 =  2*2*61 (both are 3-almost primes (A110187)).

Prog

(PARI) isok(m) = bigomega(3^m-1) == bigomega(3^m+1); \\ Michel Marcus, Dec 14 2020

Crossrefs

Cf. A001222, A057941, A057958.

Sequence in context: A136146 A289278 A167804 * A196243 A018527 A084411

Adjacent sequences: A339696 A339697 A339698 * A339700 A339701 A339702

Keyword

nonn,more

Author

Zak Seidov, Dec 14 2020

Status

approved